Lackche with Balmunk
First, you need Lackche to have major Odo blood by pairing with Holyn, or she will not be able to wield it. To start the glitch, equip Shanon with the Balmunk, and get killed. Have Corple use the Valkyrie Staff, and press L or R on Shanon. Shanon's Balmunk should change to an Iron Lance. Now Save your game, and reset. Load your game back up, and go to the Shop in your castle. Balmunk should be for sale. Now have Lackche buy it. Normally she wouldn't be able to buy it, but if you did the above steps it should work.

Access the arena unlimited times!
In chapter 7, after you defeat all of the enemies in the arena it will say that you have no one left to fight. However, if you leave your home castle and go to one of the castles you conquered, view the message that says there is no one left to fight at that castle, and then go back to your home castle, you can access the arena again. This way, you can easily get most of the second generation to level 30 in the first chapter you have them.